Preparation And Characterization Of Nano Indium-doped Zinc Oxide (ZIO) Thermal Insulation Coating

In this paper, a novel multifunctional indium-doped zinc oxide (ZIO) glass coating was prepared through two kinds of coating processs. The results show that the ZIO glass coating is transparent in the visible region and has merits of thermal insulation, self-cleaning and blocking UV light.The traditional powder-slurry-coating method was used in this paper. In this method, ZIO films were fabricated on glass substrate by the Czochralski method. The ZIO water-based paint were prepared from the ZIO powder, dispersant and waterborne polyurethane. Another approach is directional growth the ZIO nanoarrays on glass. In this approach a thin ZIO seed layer was deposited on a silicon substrate by the Czochralski method. Then uniform ZIO nanorods were grew on the seed-coated silicon substrate in aqueous solution containing indium chloride, zinc acetate dehydrate and hexamethylenetetramine (HMT).The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), zetasizer and UV-Vis spectrophotometer ect.. It was found that the ZIO with different morphologies were prepared by the precipitation method. XRD and EDX measurements confirm the incorporation of the In3+into the crystalline lattice of ZnO, and ZIO Crystalline reduced with the increase of In3+doping concentration. Microscopic particle size of ZIO samples at0.5at%and1at%In3+/Zn2+molar ratio are20nm,50nm, respectively. Laser diffraction particle size analysis indicates that the latter’s Median diameter is lower, and more evenly distributed. Transmission electron microscopy and scanning electron microscopy (TEM, SEM) measurements show that Lamellar-like, spherical-like, hexagonal columnar-like ZIO crystals, whose shapes result from the type of precipitants, and the nucleation mechanisms of ZIO with different morphologies are also discussed. It was found that the ZIO films are smooth and have characteristic of good adhesion, high transmittance in the visible region (>80%), thermal insulation and also can block UV light.In the approach of directional growth of the ZIO nanoarrays, large-scale highly oriented ZIO nanorod arrays were grown on silicon glass substrate.It was found that the reaction temperature and In-doping play an important role in preferred orientation of ZIO nanorods. When reaction temperature is under95℃the ZIO nanorods are with preferable normal c-orientation, where the c axis is perpendicular to the substrate surface. However, when the hydrothermal growth is as low as60℃, the seldom reported a//n oriented ZIO nanometer arrays are obtained, where the c axis is parallel to the substrate surface. While under the temperature the preferred orientation of ZnO nanorods parallel to the normal (c//n). ZIO films prepared through directional growth were characterized and the results show that films are transparent in the visible region and have merits of thermal insulation and block UV light. In addition those ZIO films are self-cleaning films with high hardness and excellent adhesion. ZIO films with different performances were synthesized. Compared with the c//n oriented ZIO nanoarrays, the ZIO nanoarrays with a-oriention shows better performance in areas of hardness, transparency and hydrophobic. The a//n oriented ZIO (In/Zn=2at%) is transparent in the visible region (T=84.6%) and has merits of thermal insulation, hydrophobichy(122.2°) and blocking UV light (T=16.7%), high hardness (6H) and excellent adhesion.